One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,7)(4,5)(6,8)(9,10,13,14)(11,15,16,12)(19,23)(21,24)(25,26)(27,29)(28,32)(30,34)(31,33)(35,36)(37,40)(38,39)(1,3,5,8)(2,6,4,7)(9,10)(11,12)(13,14)(15,16)(25,27)(26,31)(28,35)(29,34)(30,33)(32,38)(36,40)(37,39)(2,4)(6,7)(10,14)(12,15)(17,18,20,22)(19,21,23,24)(25,27)(26,29)(28,35)(30,33)(31,34)(32,36)(37,39)(38,40)(1,3)(2,6)(4,7)(5,8)(9,11)(10,15)(12,14)(13,16)(17,19)(18,21)(20,23)(22,24)(25,28,30,37)(26,32,34,40)(27,35,33,39)(29,36,31,38)(1,4,5,2)(3,7,8,6)(9,12,13,15)(10,11,14,16)(25,29)(26,33)(27,34)(28,36)(30,31)(32,39)(35,40)(37,38)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.